In Japanese Patent Publication No. H10-203338, a brake-by-wire vehicle brake control device is proposed which has four pumps respectively for the four wheels of a vehicle. Two of the four pumps are located in a common conduit path for two of the four wheels and are driven by a common motor. The other two of the four pumps are located in another common conduit path for the other two of the four wheels and are driven by another common motor.
The brake-by-wire vehicle brake control device drives the two motors which dominantly consume electric energy supplied from a battery. It is therefore desirable to suppress electric energy consumption of the two motors. In this aspect, it should be avoided to keep the motors always in full operation (that is, to keep the motors always in a state where they can be rotated at such a rotational speed that the pumps discharge the brake fluid at the maximum efficiency), even if keeping the motors in full operation contributes to quick response of the vehicle brake control device at the beginning of braking.
In another aspect, in order to change the W/C pressure in quick response to a driver's request for braking, it is desirable to keep the motors always in the state where they can be rotated at such a rotational speed that the pumps discharge the brake fluid at the maximum efficiency.
A method is hence necessary for achieving quick response to a request for braking made by the driver while suppressing the electric energy consumption of the motors.